Groundwater Quality

In response to a congressional request, GAO reviewed state groundwater standards activities, focusing on how states: (1) established groundwater standards; (2) set groundwater standards for specific contaminants; (3) used different standards; and (4) developed and implemented their standards.

GAO found that: (1) 41 states have numeric or narrative groundwater standards or both, while 15 states have only narrative standards; (2) states relied on federal drinking water standards for 62 percent of their numeric standards; and (3) states with additional numeric standards covered an average of 20 contaminants beyond the 34 contaminants on the federal list. GAO also found that state standards differed because: (1) background levels of contaminants were higher in some states; (2) some old standards were not updated; and (3) some states questioned the appropriateness of certain specific federal standards. In addition, GAO found that: (1) states with advanced standard-setting procedures relied on detection of contaminants before deciding to set a standard; (2) many states were constrained by inadequate technical expertise and funding; and (3) states generally used groundwater standards to issue and monitor permits.